/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.supermap.util.widget;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.SystemClock;
import android.support.v4.os.ParcelableCompat;
import android.support.v4.os.ParcelableCompatCreatorCallbacks;
import android.support.v4.view.KeyEventCompat;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.VelocityTrackerCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewConfigurationCompat;
import android.support.v4.widget.EdgeEffectCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.FocusFinder;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.animation.Interpolator;
import android.widget.Scroller;

/**
 * Layout manager that allows the user to flip left and right through pages of
 * data. You supply an implementation of a
 * {@link PagerAdapter} to generate the pages that the
 * view shows.
 *
 * <p>
 * Note this class is currently under early design and development. The API will
 * likely change in later updates of the compatibility library, requiring
 * changes to the source code of apps when they are compiled against the newer
 * version.
 * </p>
 */
public class LazyViewPager extends ViewGroup {
	private static final String TAG = "LazyViewPager";
	private static final boolean DEBUG = false;

	private static final boolean USE_CACHE = false;

	private static final int DEFAULT_OFFSCREEN_PAGES = 0;// 默认的加载页面,ViewPager是1个,所以会加载两个Fragment
	private static final int MAX_SETTLE_DURATION = 600; // ms

	static class ItemInfo {
		Object object;
		int position;
		boolean scrolling;
	}

	private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>() {
		@Override
		public int compare(ItemInfo lhs, ItemInfo rhs) {
			return lhs.position - rhs.position;
		}
	};

	private static final Interpolator sInterpolator = new Interpolator() {
		@Override
		public float getInterpolation(float t) {
			// _o(t) = t * t * ((tension + 1) * t + tension)
			// o(t) = _o(t - 1) + 1
			t -= 1.0f;
			return t * t * t + 1.0f;
		}
	};

	private final Map<Integer, ItemInfo> mItems = new HashMap<Integer, ItemInfo>();

	private PagerAdapter mAdapter;
	private int mCurItem; // Index of currently displayed page.
	private int mRestoredCurItem = -1;
	private Parcelable mRestoredAdapterState = null;
	private ClassLoader mRestoredClassLoader = null;
	private Scroller mScroller;
	private PagerObserver mObserver;

	private int mPageMargin;
	private Drawable mMarginDrawable;

	private int mChildWidthMeasureSpec;
	private int mChildHeightMeasureSpec;
	private boolean mInLayout;

	private boolean mScrollingCacheEnabled;

	private boolean mPopulatePending;
	private boolean mScrolling;
	private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;

	private boolean mIsBeingDragged;
	private boolean mIsUnableToDrag;
	private int mTouchSlop;
	private float mInitialMotionX;
	/**
	 * Position of the last motion event.
	 */
	private float mLastMotionX;
	private float mLastMotionY;
	/**
	 * ID of the active pointer. This is used to retain consistency during
	 * drags/flings if multiple pointers are used.
	 */
	private int mActivePointerId = INVALID_POINTER;
	/**
	 * Sentinel value for no current active pointer. Used by
	 * {@link #mActivePointerId}.
	 */
	private static final int INVALID_POINTER = -1;

	/**
	 * Determines speed during touch scrolling
	 */
	private VelocityTracker mVelocityTracker;
	private int mMinimumVelocity;
	private int mMaximumVelocity;
	private float mBaseLineFlingVelocity;
	private float mFlingVelocityInfluence;

	private boolean mFakeDragging;
	private long mFakeDragBeginTime;

	private EdgeEffectCompat mLeftEdge;
	private EdgeEffectCompat mRightEdge;

	private boolean mFirstLayout = true;

	private boolean isAllowScroll = true;

	private OnPageChangeListener mOnPageChangeListener;

	/**
	 * Indicates that the pager is in an idle, settled state. The current page
	 * is fully in view and no animation is in progress.
	 */
	public static final int SCROLL_STATE_IDLE = 0;

	/**
	 * Indicates that the pager is currently being dragged by the user.
	 */
	public static final int SCROLL_STATE_DRAGGING = 1;

	/**
	 * Indicates that the pager is in the process of settling to a final
	 * position.
	 */
	public static final int SCROLL_STATE_SETTLING = 2;

	private int mScrollState = SCROLL_STATE_IDLE;

	// 子控件按内容自适应高度，不是靠父控件指定
	private boolean mNeedWrapContent = false;

	/**
	 * Callback interface for responding to changing state of the selected page.
	 */
	public interface OnPageChangeListener {

		/**
		 * This method will be invoked when the current page is scrolled, either
		 * as part of a programmatically initiated smooth scroll or a user
		 * initiated touch scroll.
		 *
		 * @param position
		 *            Position index of the first page currently being
		 *            displayed. Page position+1 will be visible if
		 *            positionOffset is nonzero.
		 * @param positionOffset
		 *            Value from [0, 1) indicating the offset from the page at
		 *            position.
		 * @param positionOffsetPixels
		 *            Value in pixels indicating the offset from position.
		 */
		public void onPageScrolled(int position, float positionOffset,
                                   int positionOffsetPixels);

		/**
		 * This method will be invoked when a new page becomes selected.
		 * Animation is not necessarily complete.
		 *
		 * @param position
		 *            Position index of the new selected page.
		 */
		public void onPageSelected(int position);

		/**
		 * Called when the scroll state changes. Useful for discovering when the
		 * user begins dragging, when the pager is automatically settling to the
		 * current page, or when it is fully stopped/idle.
		 *
		 * @param state
		 *            The new scroll state.
		 * @see android.support.v4.view.ViewPager#SCROLL_STATE_IDLE
		 * @see android.support.v4.view.ViewPager#SCROLL_STATE_DRAGGING
		 * @see android.support.v4.view.ViewPager#SCROLL_STATE_SETTLING
		 */
		public void onPageScrollStateChanged(int state);
	}

	/**
	 * Simple implementation of the
	 * {@link com.mz.platform.widget.LazyViewPager.OnPageChangeListener}
	 * interface with stub implementations of each method. Extend this if you do
	 * not intend to override every method of
	 * {@link com.mz.platform.widget.LazyViewPager.OnPageChangeListener}.
	 */
	public static class SimpleOnPageChangeListener implements
			OnPageChangeListener {
		@Override
		public void onPageScrolled(int position, float positionOffset,
				int positionOffsetPixels) {
			// This space for rent
		}

		@Override
		public void onPageSelected(int position) {
			// This space for rent
		}

		@Override
		public void onPageScrollStateChanged(int state) {
			// This space for rent
		}
	}

	public LazyViewPager(Context context) {
		super(context);
		initViewPager();
	}

	public LazyViewPager(Context context, AttributeSet attrs) {
		super(context, attrs);
		initViewPager();
	}

	void initViewPager() {
		setWillNotDraw(false);
		setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
		setFocusable(true);
		final Context context = getContext();
		mScroller = new Scroller(context, sInterpolator);
		final ViewConfiguration configuration = ViewConfiguration.get(context);
		mTouchSlop = ViewConfigurationCompat
				.getScaledPagingTouchSlop(configuration);
		mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
		mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
		mLeftEdge = new EdgeEffectCompat(context);
		mRightEdge = new EdgeEffectCompat(context);

		float density = context.getResources().getDisplayMetrics().density;
		mBaseLineFlingVelocity = 2500.0f * density;
		mFlingVelocityInfluence = 0.4f;
	}

	private void setScrollState(int newState) {
		if (mScrollState == newState) {
			return;
		}

		mScrollState = newState;
		if (mOnPageChangeListener != null) {
			mOnPageChangeListener.onPageScrollStateChanged(newState);
		}
	}

	public void setAdapter(PagerAdapter adapter) {
		if (mAdapter != null) {
			mAdapter.unregisterDataSetObserver(mObserver);
			mAdapter.startUpdate(this);
			// for (int i = 0; i < mItems.size(); i++) {
			// final ItemInfo ii = mItems.get(i);
			// mAdapter.destroyItem(this, ii.position, ii.object);
			// }
			Iterator<Integer> it = mItems.keySet().iterator();
			while (it.hasNext()) {
				ItemInfo ii = mItems.get(it.next());
				mAdapter.destroyItem(this, ii.position, ii.object);
			}
			mAdapter.finishUpdate(this);
			mItems.clear();
			removeAllViews();
			mCurItem = 0;
			scrollTo(0, 0);
		}

		mAdapter = adapter;

		if (mAdapter != null) {
			if (mObserver == null) {
				mObserver = new PagerObserver();
			}
			mAdapter.registerDataSetObserver(mObserver);
			mPopulatePending = false;
			if (mRestoredCurItem >= 0) {
				mAdapter.restoreState(mRestoredAdapterState,
						mRestoredClassLoader);
				setCurrentItemInternal(mRestoredCurItem, false, true);
				mRestoredCurItem = -1;
				mRestoredAdapterState = null;
				mRestoredClassLoader = null;
			} else {
				populate();
			}
		}
	}

	public PagerAdapter getAdapter() {
		return mAdapter;
	}

	/**
	 * Set the currently selected page. If the ViewPager has already been
	 * through its first layout there will be a smooth animated transition
	 * between the current item and the specified item.
	 *
	 * @param item
	 *            Item index to select
	 */
	public void setCurrentItem(int item) {
		mPopulatePending = false;
		setCurrentItemInternal(item, !mFirstLayout && isAllowScroll, false);
	}

	/**
	 * Set the currently selected page.
	 *
	 * @param item
	 *            Item index to select
	 * @param smoothScroll
	 *            True to smoothly scroll to the new item, false to transition
	 *            immediately
	 */
	public void setCurrentItem(int item, boolean smoothScroll) {
		mPopulatePending = false;
		setCurrentItemInternal(item, smoothScroll, false);
		// 解决setCurrentItem() 空白页问题。发热量有点大？
		// requestLayout();
	}

	public int getCurrentItem() {
		return mCurItem;
	}

	public View getCurrentView() {
		return (View) mAdapter.instantiateItem(this, mCurItem);
	}

	void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
		setCurrentItemInternal(item, smoothScroll, always, 0);
	}

	void setCurrentItemInternal(int item, boolean smoothScroll, boolean always,
			int velocity) {
		if (mAdapter == null || mAdapter.getCount() <= 0) {
			setScrollingCacheEnabled(false);
			return;
		}
		if (!always && mCurItem == item && mItems.size() != 0) {
			setScrollingCacheEnabled(false);
			return;
		}
		if (item < 0) {
			item = 0;
		} else if (item >= mAdapter.getCount()) {
			item = mAdapter.getCount() - 1;
		}
		final int pageLimit = mOffscreenPageLimit;
		if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {
			// We are doing a jump by more than one page. To avoid
			// glitches, we want to keep all current pages in the view
			// until the scroll ends.
			// for (int i=0; i<mItems.size(); i++) {
			// mItems.get(i).scrolling = true;
			// }
			Iterator<Integer> it = mItems.keySet().iterator();
			while (it.hasNext()) {
				mItems.get(it.next()).scrolling = true;
			}
		}

		final boolean dispatchSelected = mCurItem != item;
		mCurItem = item;
		populate();
		final int destX = (getWidth() + mPageMargin) * item;
		if (smoothScroll) {
			smoothScrollTo(destX, 0, velocity);
			if (dispatchSelected && mOnPageChangeListener != null) {
				mOnPageChangeListener.onPageSelected(item);
			}
		} else {
			if (dispatchSelected && mOnPageChangeListener != null) {
				mOnPageChangeListener.onPageSelected(item);
			}
			completeScroll();
			scrollTo(destX, 0);
		}
	}

	ArrayList<OnPageChangeListener> listenerList = new ArrayList<OnPageChangeListener>();

	/**
	 * 扩展可实现多个监听器
	 * 
	 * @param listener
	 */
	public void setOnPageChangeListener(OnPageChangeListener listener) {
		listenerList.add(listener);
		OnPageChangeListener pageListener = new OnPageChangeListener() {

			@Override
			public void onPageSelected(int position) {
				for (OnPageChangeListener temp : listenerList) {
					temp.onPageSelected(position);
				}
			}

			@Override
			public void onPageScrolled(int position, float positionOffset,
					int positionOffsetPixels) {
				for (OnPageChangeListener temp : listenerList) {
					temp.onPageScrolled(position, positionOffset,
							positionOffsetPixels);
				}
			}

			@Override
			public void onPageScrollStateChanged(int state) {
				for (OnPageChangeListener temp : listenerList) {
					temp.onPageScrollStateChanged(state);
				}
			}
		};
		mOnPageChangeListener = pageListener;
	}

	/**
	 * Returns the number of pages that will be retained to either side of the
	 * current page in the view hierarchy in an idle state. Defaults to 1.
	 *
	 * @return How many pages will be kept offscreen on either side
	 * @see #setOffscreenPageLimit(int)
	 */
	public int getOffscreenPageLimit() {
		return mOffscreenPageLimit;
	}

	/**
	 * Set the number of pages that should be retained to either side of the
	 * current page in the view hierarchy in an idle state. Pages beyond this
	 * limit will be recreated from the adapter when needed.
	 *
	 * <p>
	 * This is offered as an optimization. If you know in advance the number of
	 * pages you will need to support or have lazy-loading mechanisms in place
	 * on your pages, tweaking this setting can have benefits in perceived
	 * smoothness of paging animations and interaction. If you have a small
	 * number of pages (3-4) that you can keep active all at once, less time
	 * will be spent in layout for newly created view subtrees as the user pages
	 * back and forth.
	 * </p>
	 *
	 * <p>
	 * You should keep this limit low, especially if your pages have complex
	 * layouts. This setting defaults to 1.
	 * </p>
	 *
	 * @param limit
	 *            How many pages will be kept offscreen in an idle state.
	 */
	public void setOffscreenPageLimit(int limit) {
		if (limit < DEFAULT_OFFSCREEN_PAGES) {
			Log.w(TAG, "Requested offscreen page limit " + limit
					+ " too small; defaulting to " + DEFAULT_OFFSCREEN_PAGES);
			limit = DEFAULT_OFFSCREEN_PAGES;
		}
		if (limit != mOffscreenPageLimit) {
			mOffscreenPageLimit = limit;
			populate();
		}
	}

	/**
	 * Set the margin between pages.
	 *
	 * @param marginPixels
	 *            Distance between adjacent pages in pixels
	 * @see #getPageMargin()
	 * @see #setPageMarginDrawable(Drawable)
	 * @see #setPageMarginDrawable(int)
	 */
	public void setPageMargin(int marginPixels) {
		final int oldMargin = mPageMargin;
		mPageMargin = marginPixels;

		final int width = getWidth();
		recomputeScrollPosition(width, width, marginPixels, oldMargin);

		requestLayout();
	}

	/**
	 * Return the margin between pages.
	 *
	 * @return The size of the margin in pixels
	 */
	public int getPageMargin() {
		return mPageMargin;
	}

	/**
	 * Set a drawable that will be used to fill the margin between pages.
	 *
	 * @param d
	 *            Drawable to display between pages
	 */
	public void setPageMarginDrawable(Drawable d) {
		mMarginDrawable = d;
		if (d != null)
			refreshDrawableState();
		setWillNotDraw(d == null);
		invalidate();
	}

	/**
	 * Set a drawable that will be used to fill the margin between pages.
	 *
	 * @param resId
	 *            Resource ID of a drawable to display between pages
	 */
	public void setPageMarginDrawable(int resId) {
		setPageMarginDrawable(getContext().getResources().getDrawable(resId));
	}

	@Override
	protected boolean verifyDrawable(Drawable who) {
		return super.verifyDrawable(who) || who == mMarginDrawable;
	}

	@Override
	protected void drawableStateChanged() {
		super.drawableStateChanged();
		final Drawable d = mMarginDrawable;
		if (d != null && d.isStateful()) {
			d.setState(getDrawableState());
		}
	}

	// We want the duration of the page snap animation to be influenced by the
	// distance that
	// the screen has to travel, however, we don't want this duration to be
	// effected in a
	// purely linear fashion. Instead, we use this method to moderate the effect
	// that the distance
	// of travel has on the overall snap duration.
	float distanceInfluenceForSnapDuration(float f) {
		f -= 0.5f; // center the values about 0.
		f *= 0.3f * Math.PI / 2.0f;
		return (float) Math.sin(f);
	}

	/**
	 * Like {@link View#scrollBy}, but scroll smoothly instead of
	 * immediately.
	 *
	 * @param x
	 *            the number of pixels to scroll by on the X axis
	 * @param y
	 *            the number of pixels to scroll by on the Y axis
	 */
	void smoothScrollTo(int x, int y) {
		smoothScrollTo(x, y, 0);
	}

	/**
	 * Like {@link View#scrollBy}, but scroll smoothly instead of
	 * immediately.
	 *
	 * @param x
	 *            the number of pixels to scroll by on the X axis
	 * @param y
	 *            the number of pixels to scroll by on the Y axis
	 * @param velocity
	 *            the velocity associated with a fling, if applicable. (0
	 *            otherwise)
	 */
	void smoothScrollTo(int x, int y, int velocity) {
		if (getChildCount() == 0) {
			// Nothing to do.
			setScrollingCacheEnabled(false);
			return;
		}
		int sx = getScrollX();
		int sy = getScrollY();
		int dx = x - sx;
		int dy = y - sy;
		if (dx == 0 && dy == 0) {
			completeScroll();
			setScrollState(SCROLL_STATE_IDLE);
			return;
		}

		setScrollingCacheEnabled(true);
		mScrolling = true;
		setScrollState(SCROLL_STATE_SETTLING);

		final float pageDelta = (float) Math.abs(dx)
				/ (getWidth() + mPageMargin);
		int duration = (int) (pageDelta * 100);

		velocity = Math.abs(velocity);
		if (velocity > 0) {
			duration += (duration / (velocity / mBaseLineFlingVelocity))
					* mFlingVelocityInfluence;
		} else {
			duration += 100;
		}
		duration = Math.min(duration, MAX_SETTLE_DURATION);

		mScroller.startScroll(sx, sy, dx, dy, duration);
		invalidate();
	}

	void addNewItem(int position, int index) {
		if (mItems.get(position) == null) {
			ItemInfo ii = new ItemInfo();
			ii.position = position;
			ii.object = mAdapter.instantiateItem(this, position);
			mItems.put(position, ii);
		}
		// if (index < 0) {
		// ItemInfo ii = new ItemInfo();
		// ii.position = position;
		// ii.object = mAdapter.instantiateItem(this, position);
		// mItems.add(ii);
		// } else {
		// mItems.add(index, mItems.get(index));
		// }
	}

	void dataSetChanged() {
		// This method only gets called if our observer is attached, so mAdapter
		// is non-null.

		boolean needPopulate = mItems.size() < 3
				&& mItems.size() < mAdapter.getCount();
		int newCurrItem = -1;
		Iterator<Integer> it = mItems.keySet().iterator();
		while (it.hasNext()) {
			ItemInfo ii = mItems.get(it.next());
			final int newPos = mAdapter.getItemPosition(ii.object);

			if (newPos == PagerAdapter.POSITION_UNCHANGED) {
				continue;
			}

			if (newPos == PagerAdapter.POSITION_NONE) {
				mItems.remove(ii);
				mAdapter.destroyItem(this, ii.position, ii.object);
				needPopulate = true;

				if (mCurItem == ii.position) {
					// Keep the current item in the valid range
					newCurrItem = Math.max(0,
							Math.min(mCurItem, mAdapter.getCount() - 1));
				}
				continue;
			}

			if (ii.position != newPos) {
				if (ii.position == mCurItem) {
					// Our current item changed position. Follow it.
					newCurrItem = newPos;
				}

				ii.position = newPos;
				needPopulate = true;
			}
		}
		// for (int i = 0; i < mItems.size(); i++) {
		// final ItemInfo ii = mItems.get(i);
		// final int newPos = mAdapter.getItemPosition(ii.object);
		//
		// if (newPos == PagerAdapter.POSITION_UNCHANGED) {
		// continue;
		// }
		//
		// if (newPos == PagerAdapter.POSITION_NONE) {
		// mItems.remove(i);
		// i--;
		// mAdapter.destroyItem(this, ii.position, ii.object);
		// needPopulate = true;
		//
		// if (mCurItem == ii.position) {
		// // Keep the current item in the valid range
		// newCurrItem = Math.max(0, Math.min(mCurItem, mAdapter.getCount() -
		// 1));
		// }
		// continue;
		// }
		//
		// if (ii.position != newPos) {
		// if (ii.position == mCurItem) {
		// // Our current item changed position. Follow it.
		// newCurrItem = newPos;
		// }
		//
		// ii.position = newPos;
		// needPopulate = true;
		// }
		// }

		// Collections.sort(mItems, COMPARATOR);

		if (newCurrItem >= 0) {
			// TODO This currently causes a jump.
			setCurrentItemInternal(newCurrItem, false, true);
			needPopulate = true;
		}
		if (needPopulate) {
			populate();
			// requestLayout();
		}
	}

	void populate() {
		if (mAdapter == null) {
			return;
		}

		// Bail now if we are waiting to populate. This is to hold off
		// on creating views from the time the user releases their finger to
		// fling to a new position until we have finished the scroll to
		// that position, avoiding glitches from happening at that point.
		if (mPopulatePending) {
			if (DEBUG)
				Log.i(TAG, "populate is pending, skipping for now...");
			return;
		}

		// Also, don't populate until we are attached to a window. This is to
		// avoid trying to populate before we have restored our view hierarchy
		// state and conflicting with what is restored.
		if (getWindowToken() == null || getParent() == null) {
			return;
		}

		mAdapter.startUpdate(this);

		final int pageLimit = mOffscreenPageLimit;
		final int startPos = Math.max(0, mCurItem - pageLimit);
		final int N = mAdapter.getCount();
		final int endPos = Math.min(N - 1, mCurItem + pageLimit);

		if (DEBUG)
			Log.v(TAG, "populating: startPos=" + startPos + " endPos=" + endPos);

		// Add and remove pages in the existing list.
		// int lastPos = -1;
		// for (int i=0; i<mItems.size(); i++) {
		// ItemInfo ii = mItems.get(i);
		// if ((ii.position < startPos || ii.position > endPos) &&
		// !ii.scrolling) {
		// if (DEBUG) Log.i(TAG, "removing: " + ii.position + " @ " + i);
		// // mItems.remove(i);
		// // i--;
		// // mAdapter.destroyItem(this, ii.position, ii.object);
		// } else if (lastPos < endPos && ii.position > startPos) {
		// // The next item is outside of our range, but we have a gap
		// // between it and the last item where we want to have a page
		// // shown. Fill in the gap.
		// lastPos++;
		// if (lastPos < startPos) {
		// lastPos = startPos;
		// }
		// while (lastPos <= endPos && lastPos < ii.position) {
		// if (DEBUG) Log.i(TAG, "inserting: " + lastPos + " @ " + i);
		// addNewItem(lastPos, i);
		// lastPos++;
		// i++;
		// }
		// }
		// lastPos = ii.position;
		// }

		// Add any new pages we need at the end.
		// lastPos = mItems.size() > 0 ? mItems.get(mItems.size()-1).position :
		// -1;
		// if (lastPos < endPos) {
		// lastPos++;
		// lastPos = lastPos > startPos ? lastPos : startPos;
		// while (lastPos <= endPos) {
		// if (DEBUG) Log.i(TAG, "appending: " + lastPos);
		// addNewItem(lastPos, -1);
		// lastPos++;
		// }
		// }
		if (mItems.get(mCurItem) == null) {
			addNewItem(mCurItem, mCurItem);
		}

		if (DEBUG) {
			Log.i(TAG, "Current page list:");
			for (int i = 0; i < mItems.size(); i++) {
				Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);
			}
		}

		ItemInfo curItem = mItems.get(mCurItem);
		// for (int i=0; i<mItems.size(); i++) {
		// if (mItems.get(i).position == mCurItem) {
		// curItem = mItems.get(i);
		// break;
		// }
		// }
		mAdapter.setPrimaryItem(this, mCurItem,
				curItem != null ? curItem.object : null);

		mAdapter.finishUpdate(this);

		if (hasFocus()) {
			View currentFocused = findFocus();
			ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused)
					: null;
			if (ii == null || ii.position != mCurItem) {
				for (int i = 0; i < getChildCount(); i++) {
					View child = getChildAt(i);
					ii = infoForChild(child);
					if (ii != null && ii.position == mCurItem) {
						if (child.requestFocus(FOCUS_FORWARD)) {
							break;
						}
					}
				}
			}
		}
	}

	public static class SavedState extends BaseSavedState {
		int position;
		Parcelable adapterState;
		ClassLoader loader;

		public SavedState(Parcelable superState) {
			super(superState);
		}

		@Override
		public void writeToParcel(Parcel out, int flags) {
			super.writeToParcel(out, flags);
			out.writeInt(position);
			out.writeParcelable(adapterState, flags);
		}

		@Override
		public String toString() {
			return "FragmentPager.SavedState{"
					+ Integer.toHexString(System.identityHashCode(this))
					+ " position=" + position + "}";
		}

		public static final Creator<SavedState> CREATOR = ParcelableCompat
				.newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() {
					@Override
					public SavedState createFromParcel(Parcel in,
							ClassLoader loader) {
						return new SavedState(in, loader);
					}

					@Override
					public SavedState[] newArray(int size) {
						return new SavedState[size];
					}
				});

		SavedState(Parcel in, ClassLoader loader) {
			super(in);
			if (loader == null) {
				loader = getClass().getClassLoader();
			}
			position = in.readInt();
			adapterState = in.readParcelable(loader);
			this.loader = loader;
		}
	}

	@Override
	public Parcelable onSaveInstanceState() {
		try {
			Parcelable superState = super.onSaveInstanceState();
			SavedState ss = new SavedState(superState);
			ss.position = mCurItem;
			if (mAdapter != null) {
				ss.adapterState = mAdapter.saveState();
			}
			return ss;

		} catch (Exception e) {
			e.printStackTrace();
			return null;
		} catch (Error e) {
			e.printStackTrace();
			return null;
		}
	}

	@Override
	public void onRestoreInstanceState(Parcelable state) {
		if (!(state instanceof SavedState)) {
			super.onRestoreInstanceState(state);
			return;
		}

		SavedState ss = (SavedState) state;
		super.onRestoreInstanceState(ss.getSuperState());

		try {
			if (mAdapter != null && mAdapter.getCount() > 0) {
				mAdapter.restoreState(ss.adapterState, ss.loader);
				setCurrentItemInternal(ss.position, false, true);
			} else {
				mRestoredCurItem = ss.position;
				mRestoredAdapterState = ss.adapterState;
				mRestoredClassLoader = ss.loader;
			}
		} catch (Exception e) {

		}
	}

	@Override
	public void addView(View child, int index, LayoutParams params) {
		if (mInLayout) {
			addViewInLayout(child, index, params);
			child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec);
		} else {
			super.addView(child, index, params);
		}

		if (USE_CACHE) {
			if (child.getVisibility() != GONE) {
				child.setDrawingCacheEnabled(mScrollingCacheEnabled);
			} else {
				child.setDrawingCacheEnabled(false);
			}
		}
	}

	ItemInfo infoForChild(View child) {
		// for (int i=0; i<mItems.size(); i++) {
		// ItemInfo ii = mItems.get(i);
		// if (mAdapter.isViewFromObject(child, ii.object)) {
		// return ii;
		// }
		// }
		Iterator<Integer> it = mItems.keySet().iterator();
		while (it.hasNext()) {
			ItemInfo ii = mItems.get(it.next());
			if (mAdapter.isViewFromObject(child, ii.object)) {
				return ii;
			}
		}
		return null;
	}

	ItemInfo infoForAnyChild(View child) {
		ViewParent parent;
		while ((parent = child.getParent()) != this) {
			if (parent == null || !(parent instanceof View)) {
				return null;
			}
			child = (View) parent;
		}
		return infoForChild(child);
	}

	@Override
	protected void onAttachedToWindow() {
		super.onAttachedToWindow();
		mFirstLayout = true;
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

		// For simple implementation, or internal size is always 0.
		// We depend on the container to specify the layout size of
		// our view. We can't really know what it is since we will be
		// adding and removing different arbitrary views and do not
		// want the layout to change as this happens.

		setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),
				getDefaultSize(0, heightMeasureSpec));

		// Children are just made to fill our space.
		mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth()
				- getPaddingLeft() - getPaddingRight(), MeasureSpec.EXACTLY);
		mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
				getMeasuredHeight() - getPaddingTop() - getPaddingBottom(),
				MeasureSpec.EXACTLY);

		// Make sure we have created all fragments that we need to have shown.
		mInLayout = true;
		populate();
		mInLayout = false;

		heightMeasureSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2,
				MeasureSpec.AT_MOST);

		// Make sure all children have been properly measured.
		final int size = getChildCount();
		int childHeight = 0;
		if (!mNeedWrapContent) {
			heightMeasureSpec = mChildHeightMeasureSpec;
		}
		for (int i = 0; i < size; ++i) {
			final View child = getChildAt(i);
			if (child.getVisibility() != GONE) {
				if (DEBUG)
					Log.v(TAG, "Measuring #" + i + " " + child + ": "
							+ mChildWidthMeasureSpec);
				child.measure(mChildWidthMeasureSpec, heightMeasureSpec);
				if (!mNeedWrapContent
						&& child.getMeasuredHeight() > childHeight) {
					childHeight = child.getMeasuredHeight();
				} else if (mNeedWrapContent && mCurItem == i) {
					childHeight = child.getMeasuredHeight();
				}
			}
		}

		if (mNeedWrapContent) {
			setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),
					childHeight);
		}
	}

	public void setNeedWrapContent(boolean need) {
		mNeedWrapContent = need;
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		super.onSizeChanged(w, h, oldw, oldh);

		// Make sure scroll position is set correctly.
		if (w != oldw) {
			recomputeScrollPosition(w, oldw, mPageMargin, mPageMargin);
		}
	}

	private void recomputeScrollPosition(int width, int oldWidth, int margin,
			int oldMargin) {
		final int widthWithMargin = width + margin;
		if (oldWidth > 0) {
			final int oldScrollPos = getScrollX();
			final int oldwwm = oldWidth + oldMargin;
			final int oldScrollItem = oldScrollPos / oldwwm;
			final float scrollOffset = (float) (oldScrollPos % oldwwm) / oldwwm;
			final int scrollPos = (int) ((oldScrollItem + scrollOffset) * widthWithMargin);
			scrollTo(scrollPos, getScrollY());
			if (!mScroller.isFinished()) {
				// We now return to your regularly scheduled scroll, already in
				// progress.
				final int newDuration = mScroller.getDuration()
						- mScroller.timePassed();
				mScroller.startScroll(scrollPos, 0, mCurItem * widthWithMargin,
						0, newDuration);
			}
		} else {
			int scrollPos = mCurItem * widthWithMargin;
			if (scrollPos != getScrollX()) {
				completeScroll();
				scrollTo(scrollPos, getScrollY());
			}
		}
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		mInLayout = true;
		populate();
		mInLayout = false;

		final int count = getChildCount();
		final int width = r - l;

		for (int i = 0; i < count; i++) {
			View child = getChildAt(i);
			ItemInfo ii;
			if (child.getVisibility() != GONE
					&& (ii = infoForChild(child)) != null) {
				int loff = (width + mPageMargin) * ii.position;
				int childLeft = getPaddingLeft() + loff;
				int childTop = getPaddingTop();
				if (DEBUG)
					Log.v(TAG,
							"Positioning #" + i + " " + child + " f="
									+ ii.object + ":" + childLeft + ","
									+ childTop + " " + child.getMeasuredWidth()
									+ "x" + child.getMeasuredHeight());
				child.layout(childLeft, childTop,
						childLeft + child.getMeasuredWidth(),
						childTop + child.getMeasuredHeight());
			}
		}
		mFirstLayout = false;
	}

	@Override
	public void computeScroll() {
		if (DEBUG)
			Log.i(TAG, "computeScroll: finished=" + mScroller.isFinished());
		if (!mScroller.isFinished()) {
			if (mScroller.computeScrollOffset()) {
				if (DEBUG)
					Log.i(TAG, "computeScroll: still scrolling");
				int oldX = getScrollX();
				int oldY = getScrollY();
				int x = mScroller.getCurrX();
				int y = mScroller.getCurrY();

				if (oldX != x || oldY != y) {
					scrollTo(x, y);
				}

				if (mOnPageChangeListener != null) {
					final int widthWithMargin = getWidth() + mPageMargin;
					final int position = x / widthWithMargin;
					final int offsetPixels = x % widthWithMargin;
					final float offset = (float) offsetPixels / widthWithMargin;
					mOnPageChangeListener.onPageScrolled(position, offset,
							offsetPixels);
				}

				// Keep on drawing until the animation has finished.
				invalidate();
				return;
			}
		}

		// Done with scroll, clean up state.
		completeScroll();
	}

	private void completeScroll() {
		boolean needPopulate = mScrolling;
		if (needPopulate) {
			// Done with scroll, no longer want to cache view drawing.
			setScrollingCacheEnabled(false);
			mScroller.abortAnimation();
			int oldX = getScrollX();
			int oldY = getScrollY();
			int x = mScroller.getCurrX();
			int y = mScroller.getCurrY();
			if (oldX != x || oldY != y) {
				scrollTo(x, y);
			}
			setScrollState(SCROLL_STATE_IDLE);
		}
		mPopulatePending = false;
		mScrolling = false;
		// for (int i=0; i<mItems.size(); i++) {
		// ItemInfo ii = mItems.get(i);
		// if (ii.scrolling) {
		// needPopulate = true;
		// ii.scrolling = false;
		// }
		// }
		Iterator<Integer> it = mItems.keySet().iterator();
		while (it.hasNext()) {
			ItemInfo ii = mItems.get(it.next());
			if (ii.scrolling) {
				needPopulate = true;
				ii.scrolling = false;
			}
		}
		if (needPopulate) {
			populate();
			requestLayout();
		}
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		/*
		 * This method JUST determines whether we want to intercept the motion.
		 * If we return true, onMotionEvent will be called and we do the actual
		 * scrolling there.
		 */

		final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;
		if (!isAllowScroll) {
			return super.onInterceptTouchEvent(ev);
		}

		// Always take care of the touch gesture being complete.
		if (action == MotionEvent.ACTION_CANCEL
				|| action == MotionEvent.ACTION_UP) {
			// Release the drag.
			if (DEBUG)
				Log.v(TAG, "Intercept done!");
			mIsBeingDragged = false;
			mIsUnableToDrag = false;
			mActivePointerId = INVALID_POINTER;
			return false;
		}

		// Nothing more to do here if we have decided whether or not we
		// are dragging.
		if (action != MotionEvent.ACTION_DOWN) {
			if (mIsBeingDragged) {
				if (DEBUG)
					Log.v(TAG, "Intercept returning true!");
				return true;
			}
			if (mIsUnableToDrag) {
				if (DEBUG)
					Log.v(TAG, "Intercept returning false!");
				return false;
			}
		}

		switch (action) {
		case MotionEvent.ACTION_MOVE: {
			/*
			 * mIsBeingDragged == false, otherwise the shortcut would have
			 * caught it. Check whether the user has moved far enough from his
			 * original down touch.
			 */

			/*
			 * Locally do absolute value. mLastMotionY is set to the y value of
			 * the down event.
			 */
			final int activePointerId = mActivePointerId;
			if (activePointerId == INVALID_POINTER) {
				// If we don't have a valid id, the touch down wasn't on
				// content.
				break;
			}

			final int pointerIndex = MotionEventCompat.findPointerIndex(ev,
					activePointerId);
			final float x = MotionEventCompat.getX(ev, pointerIndex);
			final float dx = x - mLastMotionX;
			final float xDiff = Math.abs(dx);
			final float y = MotionEventCompat.getY(ev, pointerIndex);
			final float yDiff = Math.abs(y - mLastMotionY);
			final int scrollX = getScrollX();
			final boolean atEdge = (dx > 0 && scrollX == 0)
					|| (dx < 0 && mAdapter != null && scrollX >= (mAdapter
							.getCount() - 1) * getWidth() - 1);
			if (DEBUG)
				Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + ","
						+ yDiff);

			if (canScroll(this, false, (int) dx, (int) x, (int) y)) {
				// Nested view has scrollable area under this point. Let it be
				// handled there.
				mInitialMotionX = mLastMotionX = x;
				mLastMotionY = y;
				return false;
			}
			if (xDiff > mTouchSlop && xDiff > yDiff) {
				if (DEBUG)
					Log.v(TAG, "Starting drag!");
				mIsBeingDragged = true;
				setScrollState(SCROLL_STATE_DRAGGING);
				mLastMotionX = x;
				setScrollingCacheEnabled(true);
			} else {
				if (yDiff > mTouchSlop) {
					// The finger has moved enough in the vertical
					// direction to be counted as a drag... abort
					// any attempt to drag horizontally, to work correctly
					// with children that have scrolling containers.
					if (DEBUG)
						Log.v(TAG, "Starting unable to drag!");
					mIsUnableToDrag = true;
				}
			}
			break;
		}

		case MotionEvent.ACTION_DOWN: {
			/*
			 * Remember location of down touch. ACTION_DOWN always refers to
			 * pointer index 0.
			 */
			mLastMotionX = mInitialMotionX = ev.getX();
			mLastMotionY = ev.getY();
			mActivePointerId = MotionEventCompat.getPointerId(ev, 0);

			if (mScrollState == SCROLL_STATE_SETTLING) {
				// Let the user 'catch' the pager as it animates.
				mIsBeingDragged = true;
				mIsUnableToDrag = false;
				setScrollState(SCROLL_STATE_DRAGGING);
			} else {
				completeScroll();
				mIsBeingDragged = false;
				mIsUnableToDrag = false;
			}

			if (DEBUG)
				Log.v(TAG, "Down at " + mLastMotionX + "," + mLastMotionY
						+ " mIsBeingDragged=" + mIsBeingDragged
						+ "mIsUnableToDrag=" + mIsUnableToDrag);
			break;
		}

		case MotionEventCompat.ACTION_POINTER_UP:
			onSecondaryPointerUp(ev);
			break;
		}

		/*
		 * The only time we want to intercept motion events is if we are in the
		 * drag mode.
		 */
		return mIsBeingDragged;
	}

	// 设置viewpager是否可以滑动
	public final void setSrollState(boolean scroll) {
		isAllowScroll = scroll;
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (!isAllowScroll) {
			return true;
		}
		if (mFakeDragging) {
			// A fake drag is in progress already, ignore this real one
			// but still eat the touch events.
			// (It is likely that the user is multi-touching the screen.)
			return true;
		}

		if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {
			// Don't handle edge touches immediately -- they may actually belong
			// to one of our
			// descendants.
			return false;
		}

		if (mAdapter == null || mAdapter.getCount() == 0) {
			// Nothing to present or scroll; nothing to touch.
			return false;
		}

		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(ev);

		final int action = ev.getAction();
		boolean needsInvalidate = false;

		switch (action & MotionEventCompat.ACTION_MASK) {
		case MotionEvent.ACTION_DOWN: {
			if (this.getChildCount() > 1 && !mNeedWrapContent) { // 有内容，多于1个时
				// 通知其父控件，现在进行的是本控件的操作，不允许拦截
				getParent().requestDisallowInterceptTouchEvent(true);
			}
			/*
			 * If being flinged and user touches, stop the fling. isFinished
			 * will be false if being flinged.
			 */
			completeScroll();

			// Remember where the motion event started
			mLastMotionX = mInitialMotionX = ev.getX();
			mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
			break;
		}
		case MotionEvent.ACTION_MOVE:
			if (this.getChildCount() > 1 && !mNeedWrapContent) { // 有内容，多于1个时
				// 通知其父控件，现在进行的是本控件的操作，不允许拦截
				getParent().requestDisallowInterceptTouchEvent(true);
			}
			if (!mIsBeingDragged) {
				final int pointerIndex = MotionEventCompat.findPointerIndex(ev,
						mActivePointerId);
				final float x = MotionEventCompat.getX(ev, pointerIndex);
				final float xDiff = Math.abs(x - mLastMotionX);
				final float y = MotionEventCompat.getY(ev, pointerIndex);
				final float yDiff = Math.abs(y - mLastMotionY);
				if (DEBUG)
					Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff
							+ "," + yDiff);
				if (xDiff > mTouchSlop && xDiff > yDiff) {
					if (DEBUG)
						Log.v(TAG, "Starting drag!");
					mIsBeingDragged = true;
					mLastMotionX = x;
					setScrollState(SCROLL_STATE_DRAGGING);
					setScrollingCacheEnabled(true);
				}
			}
			if (mIsBeingDragged) {
				// Scroll to follow the motion event
				final int activePointerIndex = MotionEventCompat
						.findPointerIndex(ev, mActivePointerId);
				final float x = MotionEventCompat.getX(ev, activePointerIndex);
				final float deltaX = mLastMotionX - x;
				mLastMotionX = x;
				float oldScrollX = getScrollX();
				float scrollX = oldScrollX + deltaX;
				final int width = getWidth();
				final int widthWithMargin = width + mPageMargin;

				final int lastItemIndex = mAdapter.getCount() - 1;
				final float leftBound = Math.max(0, (mCurItem - 1)
						* widthWithMargin);
				final float rightBound = Math.min(mCurItem + 1, lastItemIndex)
						* widthWithMargin;
				if (scrollX < leftBound) {
					if (leftBound == 0) {
						float over = deltaX + 200;
						// mOverscrollEffect.setPull(over / width);
						// -scrollX;
						// needsInvalidate = mLeftEdge.onPull(over / width);
					}
					scrollX = leftBound;
				} else if (scrollX > rightBound) {
					if (rightBound == lastItemIndex * widthWithMargin) {
						float over = scrollX - rightBound - 200;
						// mOverscrollEffect.setPull(over / width);
						// needsInvalidate = mRightEdge.onPull(over / width);
					}
					scrollX = rightBound;
				}
				// Don't lose the rounded component
				mLastMotionX += scrollX - (int) scrollX;
				scrollTo((int) scrollX, getScrollY());
				if (mOnPageChangeListener != null) {
					final int position = (int) scrollX / widthWithMargin;
					final int positionOffsetPixels = (int) scrollX
							% widthWithMargin;
					final float positionOffset = (float) positionOffsetPixels
							/ widthWithMargin;
					mOnPageChangeListener.onPageScrolled(position,
							positionOffset, positionOffsetPixels);
				}
			}
			break;
		case MotionEvent.ACTION_UP:
			if (mIsBeingDragged) {
				final VelocityTracker velocityTracker = mVelocityTracker;
				velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
				int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(
						velocityTracker, mActivePointerId);
				// 循环页面显示不出来修改。
				// mPopulatePending = true;
				mPopulatePending = false;
				final int widthWithMargin = getWidth() + mPageMargin;
				final int scrollX = getScrollX();
				final int currentPage = scrollX / widthWithMargin;
				int nextPage = initialVelocity > 0 ? currentPage
						: currentPage + 1;
				setCurrentItemInternal(nextPage, true, true, initialVelocity);

				mActivePointerId = INVALID_POINTER;
				endDrag();
				needsInvalidate = true;
				// mLeftEdge.onRelease() | mRightEdge.onRelease();
			}
			break;
		case MotionEvent.ACTION_CANCEL:
			if (mIsBeingDragged) {
				setCurrentItemInternal(mCurItem, true, true);
				mActivePointerId = INVALID_POINTER;
				endDrag();
				needsInvalidate = mLeftEdge.onRelease()
						| mRightEdge.onRelease();
			}
			break;
		case MotionEventCompat.ACTION_POINTER_DOWN: {
			final int index = MotionEventCompat.getActionIndex(ev);
			final float x = MotionEventCompat.getX(ev, index);
			mLastMotionX = x;
			mActivePointerId = MotionEventCompat.getPointerId(ev, index);
			break;
		}
		case MotionEventCompat.ACTION_POINTER_UP:
			onSecondaryPointerUp(ev);
			mLastMotionX = MotionEventCompat.getX(ev,
					MotionEventCompat.findPointerIndex(ev, mActivePointerId));
			break;
		}
		if (needsInvalidate) {
			requestLayout();
			// invalidate(); 空白屏幕解决。
		}
		if (mNeedWrapContent
				&& (action & MotionEventCompat.ACTION_MASK) == MotionEvent.ACTION_MOVE
				&& !mIsBeingDragged) {
			return false;
		}
		return true;
	}

	@Override
	public void draw(Canvas canvas) {
		super.draw(canvas);
		boolean needsInvalidate = false;

		final int overScrollMode = ViewCompat.getOverScrollMode(this);
		if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS
				|| (overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS
						&& mAdapter != null && mAdapter.getCount() > 1)) {
			if (!mLeftEdge.isFinished()) {
				final int restoreCount = canvas.save();
				final int height = getHeight() - getPaddingTop()
						- getPaddingBottom();

				canvas.rotate(270);
				canvas.translate(-height + getPaddingTop(), 0);
				mLeftEdge.setSize(height, getWidth());
				needsInvalidate |= mLeftEdge.draw(canvas);
				canvas.restoreToCount(restoreCount);
			}
			if (!mRightEdge.isFinished()) {
				final int restoreCount = canvas.save();
				final int width = getWidth();
				final int height = getHeight() - getPaddingTop()
						- getPaddingBottom();
				final int itemCount = mAdapter != null ? mAdapter.getCount()
						: 1;

				canvas.rotate(90);
				canvas.translate(-getPaddingTop(), -itemCount
						* (width + mPageMargin) + mPageMargin);
				mRightEdge.setSize(height, width);
				needsInvalidate |= mRightEdge.draw(canvas);
				canvas.restoreToCount(restoreCount);
			}
		} else {
			mLeftEdge.finish();
			mRightEdge.finish();
		}

		if (needsInvalidate) {
			// Keep animating
			invalidate();
			// setCurrentItem(X) 空白处理。
			// requestLayout();
		}
	}

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);

		// Draw the margin drawable if needed.
		if (mPageMargin > 0 && mMarginDrawable != null) {
			final int scrollX = getScrollX();
			final int width = getWidth();
			final int offset = scrollX % (width + mPageMargin);
			if (offset != 0) {
				// Pages fit completely when settled; we only need to draw when
				// in between
				final int left = scrollX - offset + width;
				mMarginDrawable.setBounds(left, 0, left + mPageMargin,
						getHeight());
				mMarginDrawable.draw(canvas);
			}
		}
	}

	/**
	 * Start a fake drag of the pager.
	 *
	 * <p>
	 * A fake drag can be useful if you want to synchronize the motion of the
	 * ViewPager with the touch scrolling of another view, while still letting
	 * the ViewPager control the snapping motion and fling behavior. (e.g.
	 * parallax-scrolling tabs.) Call {@link #fakeDragBy(float)} to simulate the
	 * actual drag motion. Call {@link #endFakeDrag()} to complete the fake drag
	 * and fling as necessary.
	 *
	 * <p>
	 * During a fake drag the ViewPager will ignore all touch events. If a real
	 * drag is already in progress, this method will return false.
	 *
	 * @return true if the fake drag began successfully, false if it could not
	 *         be started.
	 *
	 * @see #fakeDragBy(float)
	 * @see #endFakeDrag()
	 */
	public boolean beginFakeDrag() {
		if (mIsBeingDragged) {
			return false;
		}
		mFakeDragging = true;
		setScrollState(SCROLL_STATE_DRAGGING);
		mInitialMotionX = mLastMotionX = 0;
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		} else {
			mVelocityTracker.clear();
		}
		final long time = SystemClock.uptimeMillis();
		final MotionEvent ev = MotionEvent.obtain(time, time,
				MotionEvent.ACTION_DOWN, 0, 0, 0);
		mVelocityTracker.addMovement(ev);
		ev.recycle();
		mFakeDragBeginTime = time;
		return true;
	}

	/**
	 * End a fake drag of the pager.
	 *
	 * @see #beginFakeDrag()
	 * @see #fakeDragBy(float)
	 */
	public void endFakeDrag() {
		if (!mFakeDragging) {
			throw new IllegalStateException(
					"No fake drag in progress. Call beginFakeDrag first.");
		}

		final VelocityTracker velocityTracker = mVelocityTracker;
		velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
		int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(
				velocityTracker, mActivePointerId);
		mPopulatePending = true;
		if ((Math.abs(initialVelocity) > mMinimumVelocity)
				|| Math.abs(mInitialMotionX - mLastMotionX) >= (getWidth() / 3)) {
			if (mLastMotionX > mInitialMotionX) {
				setCurrentItemInternal(mCurItem - 1, true, true);
			} else {
				setCurrentItemInternal(mCurItem + 1, true, true);
			}
		} else {
			setCurrentItemInternal(mCurItem, true, true);
		}
		endDrag();

		mFakeDragging = false;
	}

	/**
	 * Fake drag by an offset in pixels. You must have called
	 * {@link #beginFakeDrag()} first.
	 *
	 * @param xOffset
	 *            Offset in pixels to drag by.
	 * @see #beginFakeDrag()
	 * @see #endFakeDrag()
	 */
	public void fakeDragBy(float xOffset) {
		if (!mFakeDragging) {
			throw new IllegalStateException(
					"No fake drag in progress. Call beginFakeDrag first.");
		}

		mLastMotionX += xOffset;
		float scrollX = getScrollX() - xOffset;
		final int width = getWidth();
		final int widthWithMargin = width + mPageMargin;

		final float leftBound = Math.max(0, (mCurItem - 1) * widthWithMargin);
		final float rightBound = Math
				.min(mCurItem + 1, mAdapter.getCount() - 1) * widthWithMargin;
		if (scrollX < leftBound) {
			scrollX = leftBound;
		} else if (scrollX > rightBound) {
			scrollX = rightBound;
		}
		// Don't lose the rounded component
		mLastMotionX += scrollX - (int) scrollX;
		scrollTo((int) scrollX, getScrollY());
		if (mOnPageChangeListener != null) {
			final int position = (int) scrollX / widthWithMargin;
			final int positionOffsetPixels = (int) scrollX % widthWithMargin;
			final float positionOffset = (float) positionOffsetPixels
					/ widthWithMargin;
			mOnPageChangeListener.onPageScrolled(position, positionOffset,
					positionOffsetPixels);
		}

		// Synthesize an event for the VelocityTracker.
		final long time = SystemClock.uptimeMillis();
		final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time,
				MotionEvent.ACTION_MOVE, mLastMotionX, 0, 0);
		mVelocityTracker.addMovement(ev);
		ev.recycle();
	}

	/**
	 * Returns true if a fake drag is in progress.
	 *
	 * @return true if currently in a fake drag, false otherwise.
	 *
	 * @see #beginFakeDrag()
	 * @see #fakeDragBy(float)
	 * @see #endFakeDrag()
	 */
	public boolean isFakeDragging() {
		return mFakeDragging;
	}

	private void onSecondaryPointerUp(MotionEvent ev) {
		final int pointerIndex = MotionEventCompat.getActionIndex(ev);
		final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);
		if (pointerId == mActivePointerId) {
			// This was our active pointer going up. Choose a new
			// active pointer and adjust accordingly.
			final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
			mLastMotionX = MotionEventCompat.getX(ev, newPointerIndex);
			mActivePointerId = MotionEventCompat.getPointerId(ev,
					newPointerIndex);
			if (mVelocityTracker != null) {
				mVelocityTracker.clear();
			}
		}
	}

	private void endDrag() {
		mIsBeingDragged = false;
		mIsUnableToDrag = false;

		if (mVelocityTracker != null) {
			mVelocityTracker.recycle();
			mVelocityTracker = null;
		}
	}

	private void setScrollingCacheEnabled(boolean enabled) {
		if (mScrollingCacheEnabled != enabled) {
			mScrollingCacheEnabled = enabled;
			if (USE_CACHE) {
				final int size = getChildCount();
				for (int i = 0; i < size; ++i) {
					final View child = getChildAt(i);
					if (child.getVisibility() != GONE) {
						child.setDrawingCacheEnabled(enabled);
					}
				}
			}
		}
	}

	/**
	 * Tests scrollability within child views of v given a delta of dx.
	 *
	 * @param v
	 *            View to test for horizontal scrollability
	 * @param checkV
	 *            Whether the view v passed should itself be checked for
	 *            scrollability (true), or just its children (false).
	 * @param dx
	 *            Delta scrolled in pixels
	 * @param x
	 *            X coordinate of the active touch point
	 * @param y
	 *            Y coordinate of the active touch point
	 * @return true if child views of v can be scrolled by delta of dx.
	 */
	protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
		if (v instanceof ViewGroup) {
			final ViewGroup group = (ViewGroup) v;
			final int scrollX = v.getScrollX();
			final int scrollY = v.getScrollY();
			final int count = group.getChildCount();
			// Count backwards - let topmost views consume scroll distance
			// first.
			for (int i = count - 1; i >= 0; i--) {
				// TODO: Add versioned support here for transformed views.
				// This will not work for transformed views in Honeycomb+
				final View child = group.getChildAt(i);
				if (x + scrollX >= child.getLeft()
						&& x + scrollX < child.getRight()
						&& y + scrollY >= child.getTop()
						&& y + scrollY < child.getBottom()
						&& canScroll(child, true, dx,
								x + scrollX - child.getLeft(), y + scrollY
										- child.getTop())) {
					return true;
				}
			}
		}

		return checkV && ViewCompat.canScrollHorizontally(v, -dx);
	}

	@Override
	public boolean dispatchKeyEvent(KeyEvent event) {
		// Let the focused view and/or our descendants get the key first
		return super.dispatchKeyEvent(event) || executeKeyEvent(event);
	}

	/**
	 * You can call this function yourself to have the scroll view perform
	 * scrolling from a key event, just as if the event had been dispatched to
	 * it by the view hierarchy.
	 *
	 * @param event
	 *            The key event to execute.
	 * @return Return true if the event was handled, else false.
	 */
	public boolean executeKeyEvent(KeyEvent event) {
		boolean handled = false;
		if (event.getAction() == KeyEvent.ACTION_DOWN) {
			switch (event.getKeyCode()) {
			case KeyEvent.KEYCODE_DPAD_LEFT:
				handled = arrowScroll(FOCUS_LEFT);
				break;
			case KeyEvent.KEYCODE_DPAD_RIGHT:
				handled = arrowScroll(FOCUS_RIGHT);
				break;
			case KeyEvent.KEYCODE_TAB:
				if (KeyEventCompat.hasNoModifiers(event)) {
					handled = arrowScroll(FOCUS_FORWARD);
				} else if (KeyEventCompat.hasModifiers(event,
						KeyEvent.META_SHIFT_ON)) {
					handled = arrowScroll(FOCUS_BACKWARD);
				}
				break;
			}
		}
		return handled;
	}

	public boolean arrowScroll(int direction) {
		View currentFocused = findFocus();
		if (currentFocused == this)
			currentFocused = null;

		boolean handled = false;

		View nextFocused = FocusFinder.getInstance().findNextFocus(this,
				currentFocused, direction);
		if (nextFocused != null && nextFocused != currentFocused) {
			if (direction == View.FOCUS_LEFT) {
				// If there is nothing to the left, or this is causing us to
				// jump to the right, then what we really want to do is page
				// left.
				if (currentFocused != null
						&& nextFocused.getLeft() >= currentFocused.getLeft()) {
					handled = pageLeft();
				} else {
					handled = nextFocused.requestFocus();
				}
			} else if (direction == View.FOCUS_RIGHT) {
				// If there is nothing to the right, or this is causing us to
				// jump to the left, then what we really want to do is page
				// right.
				if (currentFocused != null
						&& nextFocused.getLeft() <= currentFocused.getLeft()) {
					handled = pageRight();
				} else {
					handled = nextFocused.requestFocus();
				}
			}
		} else if (direction == FOCUS_LEFT || direction == FOCUS_BACKWARD) {
			// Trying to move left and nothing there; try to page.
			handled = pageLeft();
		} else if (direction == FOCUS_RIGHT || direction == FOCUS_FORWARD) {
			// Trying to move right and nothing there; try to page.
			handled = pageRight();
		}
		if (handled) {
			playSoundEffect(SoundEffectConstants
					.getContantForFocusDirection(direction));
		}
		return handled;
	}

	boolean pageLeft() {
		if (mCurItem > 0) {
			setCurrentItem(mCurItem - 1, true);
			return true;
		}
		return false;
	}

	boolean pageRight() {
		if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {
			setCurrentItem(mCurItem + 1, true);
			return true;
		}
		return false;
	}

	/**
	 * We only want the current page that is being shown to be focusable.
	 */
	@Override
	public void addFocusables(ArrayList<View> views, int direction,
			int focusableMode) {
		final int focusableCount = views.size();

		final int descendantFocusability = getDescendantFocusability();

		if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {
			for (int i = 0; i < getChildCount(); i++) {
				final View child = getChildAt(i);
				if (child.getVisibility() == VISIBLE) {
					ItemInfo ii = infoForChild(child);
					if (ii != null && ii.position == mCurItem) {
						child.addFocusables(views, direction, focusableMode);
					}
				}
			}
		}

		// we add ourselves (if focusable) in all cases except for when we are
		// FOCUS_AFTER_DESCENDANTS and there are some descendants focusable.
		// this is
		// to avoid the focus search finding layouts when a more precise search
		// among the focusable children would be more interesting.
		if (descendantFocusability != FOCUS_AFTER_DESCENDANTS ||
		// No focusable descendants
				(focusableCount == views.size())) {
			// Note that we can't call the superclass here, because it will
			// add all views in. So we need to do the same thing View does.
			if (!isFocusable()) {
				return;
			}
			if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE
					&& isInTouchMode() && !isFocusableInTouchMode()) {
				return;
			}
			if (views != null) {
				views.add(this);
			}
		}
	}

	/**
	 * We only want the current page that is being shown to be touchable.
	 */
	@Override
	public void addTouchables(ArrayList<View> views) {
		// Note that we don't call super.addTouchables(), which means that
		// we don't call View.addTouchables(). This is okay because a ViewPager
		// is itself not touchable.
		for (int i = 0; i < getChildCount(); i++) {
			final View child = getChildAt(i);
			if (child.getVisibility() == VISIBLE) {
				ItemInfo ii = infoForChild(child);
				if (ii != null && ii.position == mCurItem) {
					child.addTouchables(views);
				}
			}
		}
	}

	/**
	 * We only want the current page that is being shown to be focusable.
	 */
	@Override
	protected boolean onRequestFocusInDescendants(int direction,
			Rect previouslyFocusedRect) {
		int index;
		int increment;
		int end;
		int count = getChildCount();
		if ((direction & FOCUS_FORWARD) != 0) {
			index = 0;
			increment = 1;
			end = count;
		} else {
			index = count - 1;
			increment = -1;
			end = -1;
		}
		for (int i = index; i != end; i += increment) {
			View child = getChildAt(i);
			if (child.getVisibility() == VISIBLE) {
				ItemInfo ii = infoForChild(child);
				if (ii != null && ii.position == mCurItem) {
					if (child.requestFocus(direction, previouslyFocusedRect)) {
						return true;
					}
				}
			}
		}
		return false;
	}

	@Override
	public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
		// ViewPagers should only report accessibility info for the current
		// page,
		// otherwise things get very confusing.

		// TODO: Should this note something about the paging container?

		final int childCount = getChildCount();
		for (int i = 0; i < childCount; i++) {
			final View child = getChildAt(i);
			if (child.getVisibility() == VISIBLE) {
				final ItemInfo ii = infoForChild(child);
				if (ii != null && ii.position == mCurItem
						&& child.dispatchPopulateAccessibilityEvent(event)) {
					return true;
				}
			}
		}

		return false;
	}

	private class PagerObserver extends DataSetObserver {

		@Override
		public void onChanged() {
			dataSetChanged();
		}

		@Override
		public void onInvalidated() {
			dataSetChanged();
		}
	}

	// private class OverscrollEffect {
	// private float mOverscroll;
	// private Animator mAnimator;
	// private float mOverscrollAnimationDuration=400;
	//
	// /**
	// * @param deltaDistance
	// * [0..1] 0->no overscroll, 1>full overscroll
	// */
	// public void setPull(final float deltaDistance) {
	// mOverscroll = deltaDistance;
	// invalidateVisibleChilds(mCurItem);
	// }
	//
	// private void invalidateVisibleChilds(final int position) {
	// for (int i = 0; i < getChildCount(); i++) {
	// getChildAt(i).invalidate();
	//
	// }
	// // final View child = getChildAt(position);
	// // final View previous = getChildAt(position - 1);
	// // final View next = getChildAt(position + 1);
	// // if (child != null) {
	// // child.invalidate();
	// // }
	// // if (previous != null) {
	// // previous.invalidate();
	// // }
	// // if (next != null) {
	// // next.invalidate();
	// // }
	// }
	// /**
	// * called when finger is released. starts to animate back to default
	// * position
	// */
	// private void onRelease() {
	// if (mAnimator != null && mAnimator.isRunning()) {
	// mAnimator.addListener(new AnimatorListener() {
	//
	// @Override
	// public void onAnimationStart(Animator animation) {
	// }
	//
	// @Override
	// public void onAnimationRepeat(Animator animation) {
	// }
	//
	// @Override
	// public void onAnimationEnd(Animator animation) {
	// startAnimation(0);
	// }
	//
	// @Override
	// public void onAnimationCancel(Animator animation) {
	// }
	// });
	// mAnimator.cancel();
	// } else {
	// startAnimation(0);
	// }
	// }
	//
	// private void startAnimation(final float target) {
	// mAnimator = ObjectAnimator.ofFloat(this, "pull", mOverscroll,
	// target);
	// mAnimator.setInterpolator(new DecelerateInterpolator());
	// final float scale = Math.abs(target - mOverscroll);
	// mAnimator
	// .setDuration((long) (mOverscrollAnimationDuration * scale));
	// mAnimator.start();
	// }
	//
	// private boolean isOverscrolling() {
	// if (mCurItem == 0 && mOverscroll < 0) {
	// return true;
	// }
	// final boolean isLast = (getAdapter().getCount() - 1) == mCurItem;
	// if (isLast && mOverscroll > 0) {
	// return true;
	// }
	// return false;
	// }
	//
	// }
}
